A new website allows Internet users to check if their usernames and passwords were exposed in some of the largest data breaches in recent years.

The site is called haveibeenpwned.com and was created by Australian software architect Troy Hunt. It allows users to check if their email addresses are present in user databases leaked from Adobe Systems this year, Yahoo in 2012, Sony and Stratfor in 2011 and Gawker in 2010.

The Adobe data breach came to light in October and is considered to be the largest, publicly known, leak of user information in history. Over 153 million user records, including email addresses and poorly encrypted passwords, were exposed as a result of the incident.

Several security researchers created websites that allow users to check if they’ve been affected by the Adobe breach, but Hunt wanted a website that maps email addresses across multiple data breaches. This kind of correlation is important because a large number of people reuse their email addresses and passwords on multiple websites.

“No, don’t go and breach a system in order to contribute to this project!”

In 2012 Hunt compared the user records leaked from Sony and Yahoo and found that 59 percent of people with accounts in both databases used the same password.

The haveibeenpwned.com website does not store any of the leaked passwords, only the email addresses.

”I just don’t need them [the passwords] and frankly, I don’t want the responsibility either,” Hunt said in a blog post. “This is all about raising awareness of the breadth of breaches.”

Importing the data into the website was no easy task, with the Adobe database containing over 152 million records, Stratfor almost 860,000, Gawker over 530,000, Yahoo 453,000 and Sony 37,000. Hunt published a separate blog post about the technical aspects of working with the large dataset.

Combining the data into a single database also revealed some interesting statistics. “When I added the Stratfor breach to the existing Adobe records, 16% of the email addresses were already in the system,” he said. “I moved onto Sony and 17% of them were already there. Yahoo! was 22%.”

”Whilst not the chronological order in which the breaches occurred, what this demonstrated is that subsequent data sets showed a high correlation between new breach data and existing records in the system and that’s the very reason why I created this site,” Hunt said.

Hunt plans to keep adding data into the system from future data breaches and asked everyone aware of leaked user databases that are publicly available and haven’t yet been included in the project to let him know. “No, don’t go and breach a system in order to contribute to this project!” he said.

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